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Steve Withers

DMC60c Motor Stuttering

Question

Hello,

I am using the DMC60c in CAN mode and I am having trouble where I will be giving the motors a constant forward demand, but they will stop and very breifly display a white LED output, then ramp back up to speed.

Ive uploaded a video to better show the issue:
https://youtu.be/kCuTyR2KnzE

I am running 2 DMC60c devices connected to my CAN bus, the first setup with ID 0x01, the second setup with ID 0x02.

They both operate fine when connected independantly, but have this stuttering issue when both connected to the CAN bus at the same time.

Ive attached a screenshot and log of my CAN traffic. I am controlling the motors using the 0x02060001 & 0x02060002 commands for open loop voltage control of each motor.
I have checked the 0x02061400 General feedback message sent from the DMC60c, but it does not seem to give any error codes.

Help would be much appreciated.

DMC CAN traffic.PNG

DMC stop.trc

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4 answers to this question

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@Steve Withers

1. Can you confirm whether or not you have these attached to a RoboRio? I can't tell from the angle shown in your video but doesn't look like it.

2. What are you setting the vltgRampSet field to? If it's zero then what you could be seeing is a voltage dip due to high current draw during motor start up. The default value when used in PWM mode is 1024. In can mode it gets set to whatever you pass in the control frame.

3. How often is the control frame being sent? We use a heartbeat timer as a safety mechanism. If the DMC60 doesn't get a new control command within 100ms then it will assume that the robot controller died and turn off the output. Try increasing the frequency at which you send the control frame and see if that makes a difference.

Thanks,
Michael

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Hi @malexander

I don't own a RoboRio no, I am using a JETSON Nano with a USBtin to send and receive CAN messages and a STM32 that sends Joystick commands on the CAN bus.

For testing Ive set the Ramp to be very slow at only 5 ticks. I'm sending both control frames every 20 milli-seconds.

This morning I've been able to narrow down the problem to be related to my extra messages on the CAN-bus. In the picture in the first post, you can see the 0x180 message, which I use to transfer the values of some potentiometers, seems to cause a problem with the DMC60s, even through this message is completely unrelated to the DMC60 devices.

I further tested this by reducing the transmit period of this 0x180 message from 20ms down to 65ms, and the motor stuttering is drastically reduced.

I have tried changing the ID address of my extra message, but the problem seems to be just related to having the extra traffic on my CAN bus.

Is it possible that message collisions on the bus are causing problems for the DMC60c?

Thanks,
Steve

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